Phytic acid, generally accepted as having the structure myo-inositol-hexakis (dihydrogen phosphate), is a major component of plant seeds, constituting 1-3% by weight of many cereals and oil seeds. Most wheat brans contain between 4 and 5% phytic acid. Phytic acid may be prepared in pure form from various plant sources, such as wheat, corn, soybeans, sesame seeds, peanuts, lima beans, barley, oats, wild rice and sunflower seeds. It can be extracted with dilute hydrochloric acid at room temperature, precipitated with various reagents including ferric chloride, bicarbonates, potassium hydroxide, sodium hydroxide, ammonium hydroxide, calcium hydroxide, magnesium hydroxide or alcohol. It is then further purified by conventional chemical techniques.
When one or more of the acidic protons of the phosphate groups in phytic acid are replaced by a counterion, the compound is usually referred to as a phytate salt. The special name phytin is used for the calcium-magnesium salt of phytate derived from plant seeds (a product of Ciba-Geigy). The present invention includes the use not only of phytic acid and phytate salts, but also various isomeric forms of phytic acid and phytate salts. While the Anderson structure for myo-inositol hexakis dihydrogen phosphate is the accepted structure for phytic acid, the present invention covers other isomers which have been previously described in the literature. These isomers include the cis, epi, allo, muco, neo, D-chiro, L-chiro, and scyllo configurations.
Also, while phytic acid contains six phosphate groups, when introduced into the digestive tract of an animal, one or more of the phosphate groups may be hydrolyzed by the action of the digestive acids and enzymes. Therefore, the present invention includes the use of hydrolysates of phytic acid and phytate salts wherein one or more of the phosphate groups have been removed.
The main uses of phytic acid include use as a food additive for preservation of foods. Studies on the use of phytic acid as a food additive show that ingestion of large doses of phytic acid elicits no physiological discomfort or symptoms of any toxicological action in humans. See Starkenstein, Biochem. Z. 30: 56 (1911). Phytic acid and its metabolites are thus not believed to be toxic or highly reactive.
Medical applications of phytic acid include use as an imaging agent for organ scintography, an X-ray enhancement contrasting agent and use to reduce gastric secretion for treatment of gastritis, gastroduodenitis, gastric duodenal ulcers and diarrhea. It has been suggested as an antidote for toxic metal absorption, for therapeutic use in the prevention and dilution of calcium deposits associated with various diseases and for reducing calcium concentration in urine (thus checking the formation of renal calculi). Other uses include as a preventive agent against severe poisoning with pressurized oxygen and preventing thirst during exercise. It has been used as a counterion in salts with various orally administered antibiotics to improve taste.
Phytic acid has also been suggested to reduce the incidence of dental caries, and has been utilized in dentifrices, mouth rinses, dental cements, cleaning agents for dentures and for removing nicotine tar from teeth.
Industrial uses of phytic acid include use as a corrosion inhibitor on metals, a rust remover and an additive to lubricating greases. Other miscellaneous uses of phytic acid include oral administration to treat acne, to improve skin color, blood circulation and fingernail growth; and as an additive in cosmetics for anti-dandruff hair lotions and skin care lotions. One potential agricultural use of phytic acid is to inhibit aflatoxin production by Asperoillus parasiticus. It is also useful as an additive to a fermentation medium containing Micromonospora sagamiensis in the fermentative production of antibiotics. Similarly, phytic acid may be used as a growth-promoting factor in the fermentation medium for the cultivation of yeast for feed.
For further discussions of industrial applications of phytic acid, see Graf, JAOCS 60, 1861-1867 (1983).
Although the above description indicates the broad scope of potential uses of phytic acid, there is not believed to be any suggestion in the prior art that phytic acid is useful for the inhibition of tumor growth.
Accordingly, it is an object of the present invention to provide a method for inhibiting tumor growth by use of phytic acid, phytate salts, and isomers or hydrolysates thereof.